# What's the suitable specifications for the FIR filter?

i have EEG signal,the sampling frequency is 256 HZ .The wavelet decomposition that i will use does not allow the extraction of specific frequency bands without additional filtering. Thus, in order to correlate the wavelet decomposition with the five sub-bands of the EEG signal,the frequency content segments of the EEG signal was restricted to the 0-64 Hz band by convolving the signal with a low-pass finite impulse response (FIR) filter.So when i try to design the FIR filter using MATLAB i want to know how to choose the suitable specifications.

thanks

• Well, sounds like you want to pass 0 to 64 Hz with minimum distortion and reject after that out to your sampling frequency limit (and hope that a suitable analog filter was used prior to sampling). The trade space is the transition band; the longer the filter the sharper the transition band. How much rejection you need in the stop band, and how steep you need the transition band depends entirely on the noise level you expect in those areas, and what your final SNR requirements are in your processed signal. You can take an FFT of your signal prior to filtering to assess the noise level. – Dan Boschen Mar 21 '17 at 16:30
• this is the code that i used to design the FIR filter si would like to know how to choose the correct specifications of the filter ? clc; clear all; close all; load('C:\Users\del.dell-PC\pfe\base de donnée\patient sans crise\chb01_01_edfm.mat') deriv1=(val(1,:)-0)/2.559375; Fs=256; t1=(0:length(deriv1)-1)/Fs; d1=designfilt('lowpassfir','PassbandFrequency',0.45,'StopbandFrequency',0.5,'PassbandRipple',3,'StopbandAttenuation',60,'DesignMethod','equiripple'); a = filtfilt(d1,deriv1); – afef Mar 21 '17 at 18:21
• That is quite a broad question; what specifically is confusing you with Matlab's help? – Dan Boschen Mar 21 '17 at 18:25
• i want to know how to choose the passband ripple and the stop band attenuation if i just know the sampling frequency and i want to restrict my signal in the band 0-64HZ – afef Mar 21 '17 at 18:31
• www.mathworks.com/help/signal/ref/designfilt.html please read that as it has the info you are looking for- something in there may confuse you which we can then likely help you with – Dan Boschen Mar 21 '17 at 18:33